The root of Zingiber officinale R. was extracted with 80% aqueous MeOH, and the concentrated extract was fractionated with EtOAc, n-BuOH and water phases. The EtOAc fraction exhibited most potent antioxidant activity among them, and two active compounds were isolated by activity-guided separation using repetitive silica gel column chromatography. On the bases of spectral data and the chemical characteristics, the structure of the compounds were determined as 6-shogaol and 12-shogaol, respectively. The EC_(50) values of them were evaluated as 26.4 ¥ìM and 22.5 ¥ìM, respectively, where these values were higher than the commercial antioxidants, such as, BHA, BHT and ¥á-tocopherol.
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